docs: def export(self, nidm_version, export_dir):
          """
          Create prov entities and activities.
          """
          attributes = [(PROV['type'], self.drift_type),
                        (PROV['label'], self.label)]
  
          if self.drift_type == FSL_GAUSSIAN_RUNNING_LINE_DRIFT_MODEL:
              attributes.append((FSL_DRIFT_CUTOFF_PERIOD, self.parameter))
  
          if self.drift_type == SPM_DCT_DRIFT_MODEL:
              attributes.append((SPM_SPMS_DRIFT_CUT_OFF_PERIOD, self.parameter))
  
          # Create "drift model" entity
          self.add_attributes(attributes)